A method of determining the moisture content of material on a bobbin featuring a hollow core, the method comprising the steps of: (a) transmitting a plurality of microwaves substantially through a portion of the bobbin, such that the microwaves are transmitted microwaves; (b) receiving the transmitted microwaves such that the microwaves are received microwaves; (c) determining a phase shift and an attenuation from the received microwaves; (d) repeating steps (a) to (c) for at least a portion of the material on the bobbin, such that a plurality of phase shifts and a plurality of attentuations is obtained; (e) using at least one empirical factor selected from the group consisting of weight of the bobbin, temperature of the bobbin, shape of the bobbin and type of the material to correct the plurality of attenuations, producing a plurality of corrected attenuations; (f) calculating a raw moisture content of the material from the corrected attenuations; (g) correcting the plurality of phase shifts for an artefact caused by the hollow core, such that the plurality of phase shifts becomes a plurality of corrected phase shifts; (h) determining a density of the material from the corrected phase shifts; and (i) calculating a final moisture content of the material from the density and from the raw moisture content.